1. Field of the Invention
This invention relates to electrical switches and to electrical apparatus including an electrical switch. Particularly, but not exclusively, the apparatus to which the invention relates is a timer device including an electrical switch.
The purpose of a switch is to selectively make or break an electrical circuit. In the past, a vast range of devices has been proposed which serve this purpose.
2. Summary of the Prior Art
Most commonly, a switch is a discreet component that is connected within a circuit during manufacture of an electrical apparatus. Switches of this type often make up a disproportionately large part of the cost of the electrical apparatus of which they are a part because they are expensive components (when compared with, for example, resistors, capacitors and many semiconductor devices) and because their connection within the apparatus adds an extra manufacturing step. Often, such switches fail earlier than other components of an electrical apparatus. This is particularly so where the apparatus operates in a hostile environment because many types of switches cannot be completely sealed against eternal contamination without leading to substantial expense.
One known type of switch comprises two or more exposed conductive pads formed on a printed circuit board, onto which a conductive element can be pressed to complete an electrical circuit between them. The conductive element is typically a graphite-loaded or metallised button, part of which projects from a housing. A user can press on the button to complete the circuit. Such switches are advantageously simple to manufacture, but nonetheless still require an additional component to be provided (the button) and can be subject to contamination where the button projects from the housing.